1. Field of the Invention
The present invention generally relates to a film packaging machine that comprises two rollers on opposite sides of a cylindrical member over which a tubular packaging film is fit for physically engaging and driving the film, and in particular to an adjusting device for adjusting the distance between the rollers to accommodate tubular film sections of different dimensions.
2. The Related Art
Heat-shrinkage films are widely used to package a variety of consumer products, such as beverage bottles/jars, food cans, optic disc packs, and even books, and to provide a surface cover of these consumer products with information or patterns, such as advertisements and decorations, printed or otherwise formed thereon. The films are often made in a length of tube that is then expanded by a packaging machine for fitting over an article to be packaged. Heat is then applied to shrink and the film for tightly wrapping around the article.
The conventional film packaging machine is often a bulky facility combined in a production line. The film packaging machine must be adjusted for films of different sizes that are used to package article of different sizes. The adjustment is cumbersome and complicated, which leads to high expenses.
Taiwan Patent Publication No. 211592 and U.S. Pat. No. 5,791,220 both disclose a film packaging machine comprising a flexible coupling connected to two film drive rollers in order to allow lateral adjustment of distance between the rollers. However, the adjustment is limited to the flexibility of the coupling and large distance adjustment is not possible. This is not helpful in accommodating the packaging machine to films of widely varied sizes. Further, the coupling is easily damaged due to fatigue. Constant maintenance is required, which leads to a great amount of maintenance expense. Further, the forces applied to the film by the rollers are not uniform, which leads to un-smooth movement of the film and wrinkling of the film when the film is fit over the article to be packaged.
Other references, such as UN Patent No. 5,531,858, disclose facility and technology for adjusting the diameter of the member over which the tubular film is fit, which comprises a complicated transmission for the film drive rollers that drives the film. Again, the force applied to the film by the rollers is not uniform, leading to un-smooth movement and wrinkling of the film.
It is thus desired to provide a device for adjusting the film drive rollers of the film packaging machine that also provides smooth movement of the film by applying uniform driving force to the film, in order to overcome the problems encountered in the prior art.